An input device for inputting information to a remote electronic device, such as a display device, has been proposed. The input device has an operating member to be operated by a user. For example, the input device is employed to move a cursor such as a pointer on a display screen of the display device. The cursor can be moved in association with an operation of the operating member.
In such an input device, an operating member is, for example, supported to be movable in arbitrary directions along a XY plane including an X axis and a Y axis and rotatable about a Z axis. Further, it has been proposed to support the operating member so that a tactile feeling is provided in accordance with an operation condition of the operating member so as to improve user's confirmation of the operation.
In order to make such an input device compact and reduce manufacturing costs, an input device using an electromagnetic force has been proposed. For example, a haptic input device described in U.S. Pat. No. 7,176,892 (corresponding to JP3934394B2) includes: a supporting member having a spherical bearing; a lever handle having a spherical portion to be supported by the spherical bearing; an electromagnetic coil arranged to oppose a lower end surface of the lever handle; a detecting unit for detecting an operating state of the lever handle; and a control unit for receiving a signal from the detecting unit and outputting a driving signal of the electromagnetic coil based on the signal of the detecting unit. The lever handle is rockably and rotationally mounted to the supporting member.
The lower end surface of the lever handle is spherical. A magnetic plate is provided entirely along the spherical end surface of the lever handle through a lead spring. The electromagnetic coil is arranged to oppose the magnetic plate when the lever handle is at the stationary position, that is, when the lever handle is not displaced. The electromagnetic coil and a lining material provided on an upper surface of the electromagnetic coil cooperate with the magnetic plate to constitute an electromagnetic brake.
In the haptic input device described in U.S. Pat. No. 7,176,892, a feeling of resistance that varies in intensity depending upon the amount of rotation is applied to the lever handle. Thus, the user can learn by blind touch whether or not the lever handle has been rotationally operated by the intended amount of rotation.
In U.S. Pat. No. 7,176,892, however, the operation thereof is not described in detail. Further, the electromagnetic coil is provided in the form of ring. Thus, when the lever handle is at the stationary position, the electromagnetic coil is opposed to a peripheral area of the magnetic plate. In other words, it appears that the electromagnetic coil is still opposed to the magnetic plate even if the lever handle is rotated, and an opposing area between the ring-shaped electromagnetic coil and the magnetic plate does not change.
Thus, as the amount of rotation is increased, an attracting magnetic force (Coulomb force) exerted between the electromagnetic coil and the magnetic plate is increased by increasing an electric current (driving signal) passing through the electromagnetic coil, thereby to strongly urge the spherical end surface of the lever handle to the spherical bearing of the supporting member. It is surmised that the resistance against the rotational motion is increased by such a structure.
To provide a user with a favorable tactile feeling, that is, to improve the confirmation of the operation, it is has been proposed to apply an external force to the operating member in a direction along a direction of displacement (operating direction). For example, if an external force is applied in the direction of the displacement, an acceleration feeling is provided. If an external force is applied in a direction opposite to the direction of the displacement, a brake feeling is provided. Preferably, the external force in the direction opposite to the direction of displacement is applied.
In the haptic input device of U.S. Pat. No. 7,176,892, the tactile feeling of the lever handle is provided by the attracting magnetic force (Coulomb force) exerted in a direction along the axis of rotation of the lever handle. That is, the external force is applied in a direction perpendicular to the direction of rotation, not in a direction along the direction of rotation. Therefore, it may be difficult to provide the tactile feeling. To provide a favorable tactile feeling, that is, to improve the confirmation of the operation in such a case, it is necessary to increase the resistance by increasing the electric current passing through the electromagnet.